the effect of calcium silicate on cation exchange capacity
TRANSCRIPT
THE EFFECT OF CALCIUM SILICATE ON CATION EXCHANGE CAPACITY AND ON EXCHANGEABLE POTASSIUM, CALCIUM AND MAGNESIUM
IN A FIELD TRIAL ON A HYDRIC DYSTRANDEPT
A THESIS SUBMITTED TO THE GRADUATE DIVISION OF THE UNIVERSITY OF HAWAII IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OFMASTER OF SCIENCE
IN AGRONOMY AND SOIL SCIENCE
MAY 1973
ByRaymond S. Uchida
Thesis Committee:Yusuf N. Tamimi, Chairman Richard E. Green Yoshinori Kanehiro
We certify that we have read this thesis and that in our
opinion it is satisfactory in scope and quality as a thesis for the degree of Master of Science in Agronomy and Soil Science.
Thesis Committee
t*/. ^Chairman
X I
TABLE OF CONTENTS
PageLIST OF TABLES............................................ iii
LIST OF ILLUSTRATIONS ..................................... ivINTRODUCTION........................•..................... 1
REVIEW OF LITERATURE....................................... 2MATERIALS AND METHODS..................................... 6
RESULTS.................................................. 11DISCUSSION................* .............................. 24SUMMARY AND CONCLUSION..................................... 29
APPENDIX.................................................. 31LITERATURE CITED............... 50
I l l
LIST OF TABLES
Table Page
1 The Effect of CaSiO^ on CEC with Depth................ 14
2 The Effect of pH of N NH.OAc on CEC,Extraction of Cations and Silicon.............. 22
3 Profile Description of the Maile Silty Clay Loam....... 324 Chemical Analyses of the Maile Silty Clay Loam......... 35
5 The Effect of CaSiOj on Soil pH with Depth............. 376 The Effect of CaSiOj on Exchangeable K with Depth . . . . 387 Percent of Total Exchangeable K in each
Treatment Profile................................. 39
8 The Effect of CaSiO^ on Exchangeable Ca with Depth . . . . 409 Percent of Total Exchangeable Ca in each
Treatment Profile................................. 41
10 The Effect of CaSiO^ on Exchangeable Mg with Depth . . . . 4211 Percent of Total Exchangeable Mg in each
Treatment Profile................................. 4312 The Effect of CaSiO, on Water-extractable
Silicon with Depth ................................ 4413 Percent of Total Water-extractable Silicon
in each Treatment Profile.......................... 4514 The Effect of CaSiO, on the Average pH, CEC,
Exchangeable Ca and"T4g, and Water-extractableSi of a Profile................... 46
15 The Effect of CaSiO, on the Distribution of Exchangeable Ca, Mg, K and Water-extractableSilicon in a Profile..................... 47
16 Percent Moisture in Soil............................. 4817 Extractable Soil P by the Modified Truog Method........ 49
LIST OF ILLUSTRATIONS
Figure Page1 Effect of CaSiO, on Soil pH at Different
Soil Depths.......................................... 13
2 Effect of CaSiO, on Exchangeable Potassiumat Different Soil Depths . . . ...................... 15
3 Effect of CaSiO, on Exchangeable Calcium atDifferent Soil Depths................................. 17
4 Effect of CaSiO, on Exchangeable Magnesiumat Different Soil Depths............................. 19
5 Effect of CaSiO, on Water-extractable Siliconat Different Soil Depths............................. 21
6 X-ray Diffraction of the Maile Silty ClayLoam Profile........................................ 36
iv
INTRODUCTION
The soil from the Hamakua Experimental Farm, which is located on the
humid Hamakua coast on the island of Hawaii, is derived from volcanic ash.
Such soils derived from volcanic ash in the humid tropics are usually of agricultural importance.
The environmental conditions found on the Hamakua coast are favorable for the rapid alteration of the parent material. In this period of alteration, the ash soil loses most of its bases and will result in the accumulation of hydrated iron and aluminum oxides. As a result of this leaching of bases and the presence of iron and aluminum
oxides, the soil tends to become acidic. This condition leads to changes in the availability of mineral nutrients and the soil also becomes generally unfit for good crop production.
Liming has long been the agricultural practice used in improving the pH in acid soils. Raising the pH of acid soils may increase the
availability of several mineral nutrients and depress the solubility of elements which are toxic. Aside from raising the pH to a range better
suited to crop nutrition, liming materials, such as CaCO^ and CaSiO ,
also replenishes the calcium in calcium deficient soils.The research reported here was designed to evaluate the effect of
calcium silicate on: (a) soil pH and its relation to cation exchangecapacity and (b) retention of exchangeable potassium, calcium, magnesium, and water-extractable silicon in the upper horizons of a Hydric Dystrandept profile.
REVIEW OF LITERATURE
I. Soil Acidity
Volcanic ash soils that have been exposed to intense weathering,
lose most of their bases, while the hydrogen ion is accumulated in the
presence of hydrous oxides of aluminum and iron. Following a stepwise hydrolysis, aluminum and iron compounds cause the release of H+ ions which then lower the soil pH. Hough, et al. (17) reported that the Hilo and Hamakua coastal soils suffered heavy losses of bases and silica while accumulating aluminum and iron within the profile.
Burgess (9) showed that the solubility of aluminum is related to pH, and he classified acidic soils of Hawaii in groups characterized by:(a) high acidity (pH 4.0-5.0) with active alumina of about 388 ppm and(b) low acidity (pH 5.0-5.8) with active alumina of about 36 ppm.
Magistad (24) confirmed that the solubility of aluminum is related to pH. Paver and Marshall (32) stated that aluminum acts as an exchangeable base
and may occupy a number of exchangeable sites in an acidic soil. This
would lower the number of exchangeable sites available for basic cations and cause a subsequent decrease in base exchange capacity of the soil.
II. Soil pH and Cation Exchange CapacityDue to the great reactivity of the amorphous fraction which
possesses highly specific surface charges, soils originating from volcanic ash exhibit peculiar properties (23). Swindale (40) reported
that it is unusual to find pH values below 5.0 in volcanic ash soils because of the high buffering capacity of allophane in the region of its
iso-electric point or the high buffering capacity of polymerized alumina
gels. Birrell and Gradwell (7) reported that when the cation exchange
capacity of allophanic soils was determined, variation in results were
due to: (a) the concentration of the leaching solution, (b) the type of
ions in the leaching solution, and (c) the volume of the washing alcohol.Birrell (6) and Wada and Ataka (46) showed that CEC in allophane
has values which are attributed to both permanent charges and pH-
dependent charges. Hough, et al. (17) and Coleman, et al. (10) indicated that CEC in allophanic clays is caused by permanent charges
which would arise from isomorphous substitution in the clay lattice. Contrary to permanent charge CEC, Hanna and Reed (15), Davis (11), Pratt and Hollowaychuk (34), and Pratt (33) illustrated the dependence of the cation exchange capacity on the pH of soils by using different methods of measurement. Schofield (85), showed that the negative charge on a subsoil was partially pH dependent.
Several investigators (16, 26, 27) showed that the CEC contributed
by organic matter and clay varies at different soil pH values. Bartlett and McIntosh (3) and McLean, et al. (27) suggested that most of the increase in CEC resulting from liming was due to organic exchange sites previously inactivated by Al+++ ions. Greenland (14) proposed a
mechanism by which organic materials could be bonded to clay particles when iron and aluminum hydroxides are polymerized at the clay surfaces,
de Villiers and Jackson (12) also found an increase in CEC as a result of increased soil pH in moderately to highly weathered acid soils.
3
III. Liming EffectsIn agricultural practices, application of liming materials has been
the main method of raising soil pH. Voelcher (45) reported that liming
with slag had a more lasting effect on soil reaction than quicklime.
Application of calcium silicate has also been shown to have significant
effects on crop yield (29, 37, 39). Increasing rates of calcium silicate
also caused an increase in pH in sane tropical soils (25, 29, 39).
A. Effect on cation exchange capacity
Onikura (31) and Tamimi, et al. (42) showed that cation exchange capacity increased with increasing rates of CaSiO^ application.Onikura (31) concluded that the increase of cation exchange capacity in the surface soil was due mainly to the formation of stable amorphous
aluminum silicate and not to the quantity or quality of the humus present. He also showed that the polymerization of silica increases the cation exchange capacity in an alkaline medium.
B. Effect on basic cationsWith this increase in cation exchange capacity in the surface soils,
it would be reasonable to expect greater retention of the cations.Ayres (1) demonstrated that potassium leached most slowly from limed
latosols as compared to the unlimed latosols. Mahilum, et al. (25) showed an increase in retention of potassium, calcium and magnesium in a Hydro Humic Latosol profile with increasing rates of calcium silicate (slag). Seatz and Winters (36) also found that there was greater
potassium retention when calcium rather than hydrogen was the
4
complementary ion. Syed-Fadzil (41) concluded that cation leaching decreased with increasing calcium silicate. It has been inferred that seme exchange sites are specific adsorption sites for potassium (4, 8).
Greater retention of potassium has also been found to be influenced by
anion adsorption (2, 28). A thorough review of potassium and the
factors that affect its movement in soils is given by Munson and Nelson (30).
5
MATERIALS AND METHODS
A. Soil Sampling Site and Soil Description
The sampling site for this experiment was the Hamakua ExperimentalFarm on the island of Hawaii, which is located at an elevation of 762 meters and has a mean annual rainfall of 230 centimeters. The mean annual maximum and minimum temperatures are 21.4 C and 14.0 C
respectively. The soil is a silty clay loam which belongs to the Maileseries, a Hydric Dystrandept developed from volcanic ash. The profile description of the Maile silty clay loam has been given by Uehara, et al. (43) (Table 3 in the Appendix).
Under virgin conditions, the Maile silty clay loam possesses the chemical analysis as described by Ikawa (19) (Table 4 in the Appendix).
The X-ray diffraction patterns for the whole soil of the profile,
illustrate an increase of amorphous material with increasing depth. The major crystalline peaks are quartz and magnetite (Fig. 6 in the Appendix).
B. Field Plots
The soil samples under investigation were collected from fertility plots that were established in 1967 for a 5 x 5 factorial on P X CaSiOg with three replications. Prior to the planting of corn, Zea mays L.
(cultivar ITWaimea Dent"), commercial calcium silicate was applied at rates of 0, 6.72, 13.44, 26.88 and 53.76 metric tons/hectare. This
material has an analysis of 32.61 Ca, 22.21 Si, 0.041% K, and 0.022% P.The material was broadcast by hand on plots that measured 7.28 x 14.56 meters, and disc-plowed. Two weeks later, phosphorus was applied at the
rates of 0, 84, 168, 336, and 672 kilograms/hectare, as treble
superphosphate, along with 84 kg N/ha, 336 kg K/ha, 134 kg Mg/ha and
45 Zn/ha. An additional 252 kg N/ha was applied during the growth of
the plants. The second crop of com (1968) received the same amount of
N, P, and K along with 17 kg Cu/ha. A third crop of corn was planted during 1969, and received 364 kg N/ha, 336 kg K/ha and 134 kg Mg/ha.
Following a year of fallow (1970), a crop of Irish potatoes,Solanum tuberosum (var. 35-S), was planted in 1971 with the followingnutrients applied: 336 kg N/ha, 336 kg K/ha, 22 kg B/ha and 11 kgCu/ha.
C. Soil Sampling ProcedureA previous study on the same soil by Tamimi, et al. (42) showed no
effect of phosphorus rates on soil cation exchange capacity.Subsequently samples were taken from plots that received a total of
672 kg P/ha at all rates of CaSiO^ from all three replicates. Samples
were obtained with a 10 cm diameter soil auger at 12 cm depth intervals, down to a depth of 91 cm. Extreme precautions were taken to avoid contamination by having the auger washed before sampling each layer.
Soil samples from each layer were placed in double plastic bags and were taken to the laboratory where they were mixed thoroughly. A sub-sample was taken from each bag and was passed through a 20 mesh sieve.
D. Methods of Chemical Analyses
Chemical analyses were conducted to determine soil pH, CEC, exchangeable K, Ca, and Mg, extractable P and water extractable silicon.
7
Cation exchange capacity was determined by saturating the soil with N
NH^OAc adjusted to the pH of the soil as suggested by Tamimi, et al. (42).
1) Soil Moisture
Approximately 10 g of soil were placed in moisture cans,
and soil moisture was determined by oven diying overnight at 105 C.
2) Soil pHApproximately 15 g of soil were mixed with water in
portion cups until a paste was formed. One hour was allowed
for equilibration and the pH was determined using glass electrodes with a Beckman Expandomatic pH meter.
3) Cation Exchange Capacity
To 10 g (oven dry equivalent) of each soil sample, 200 ml
of N NH^OAc, adjusted to the pH of the soil were added and shaken in 500 ml Erlenmeyer flasks for 1 hour. Using vacuum suction, filtration was carried out with a Buchner funnel using Whatman No. 42 filter paper. The soil was washed with four 50 ml increments of N NH^QAc, which had been adjusted to the pH of the soil, to completely saturate the soil cation exchange sites with ammonium ions. The filtrate and washings were saved for the determination of exchangeable cations. The soil retained on the filter paper was then washed with 200 ml of 95% ethyl alcohol in 50 ml aliquots. The washed soil and filter paper were then transferred to a 500 ml Erlenmeyer flask to which 200 ml of N KC1 was added and shaken for one hour.
8
Using vacuum suction the soil was filtered and washed with
another 200 ml KC1 in 50 ml portions. The filtrate plus washings were transferred to 800 ml Kjeldahl flasks. A few drops of mineral oil, pieces of mossy zinc, glass beads and magnesium oxide were added. The'NH^ was distilled into 150 ml
of saturated boric acid with several drops of mixed indicator (methylene blue and methyl red) until two-thirds of the
extract was distilled. Standard sulfuric acid was used to
titrate the distillate.
4) Exchangeable calcium, magnesium and potassiumUsing the N NH^OAc extract from the CEC determination,
the cations were determined using the Perkin-Elmer model 209
atonic absorption spectrophotometer. To prevent interferences by other ions, the extract for each sample was diluted with0.21 lanthanum oxide.
5) Water extractable siliconTen grams (oven dry equivalent) of soil were placed in 500
ml Erlenmeyer flasks and shaken for one hour with 200 ml of distilled water. After shaking, the solution was centrifuged
at 1800 rpm for 15 minutes then filtered through a Whatman No.
42 filter paper.Ammonium molybdate in sulfuric acid was added to an
aliquot of the extract in 50 ml volumetric flasks to form a
yellow silicomolybdate complex which was reduced to molybdenum blue (22). Color intensity was read on a Klett-Summerson
9
colorimeter with a 660 my filter.10
E. Statistical Analysis
Analysis of variance was performed according to Snedecor (38) and significant differences between treatment means were determined using the Modified Duncan's (Bayesian) Least Significant Difference Test (13).
RESULTS
Effect of CaSiOj rates on soil pH and CEC in the soil profile
1) Soil pH
The various application rates of CaSiO3 increased the pH of the soil. As the rates were increased from 0 to 53.76 metric tons of CaSiO^ per hectare, the average pH within the soil profile increased significantly from 5.35 to 6.04
respectively (P<.05) (Table 5 in Appendix). The relatively small change in pH with this large amount of CaSiO^ indicates that the soil is very highly buffered. These differences were
significant over all rates except between 6.72 and 13.44 metric tons of CaSiOj per hectare treatments. The effect of CaSiO^
throughout the profile is shown in summary in Fig. 1 and Table 5 in the Appendix. The pH is shown to increase significantly
(P<.05) with increasing rates of CaSiOj down to 30 cm. Below this depth, only the 53.76 tons/ha CaSiO^ treatment has pH values that are consistently higher than all of the other treatments.
At the 0 and 6.72 tons/ha CaSiO^ treatments, the pH increased significantly with depth. The pH in the 13.44 and26.88 tons/ha CaSiO^ profile remained fairly constant but the
53.76 tons/ha CaSiC^ shows some significant decreases of pH with depth. However, at lower depths of 61-91 cm, inherent
properties of the soil probably come into the picture. With the 26.88 and 53.76 tons CaSiOg treatments, the pH was higher
at the surface than the underlying layers (Fig. 1).
2) Cation Exchange capacity of the soil
The cation exchange capacity of the soil increased
significantly with applications of CaSiO^ (Table 1). As the rate of application was increased frcm 0 to 53.76 tons CaSiO^, the CEC increased from 48.63 to 63.65 me/100 g respectively, in
the surface 15 cm. There was also a significant difference in CEC between the 6.72 and the 53.76 tons application rates down
to 30 cm. Although there is a noticeable difference in CEC with the 53.76 tons treatment from all other treatments at the
0-30 cm depth, no statistically significant differences were found between all treatments below 30 cm. There was also a significant difference between the 53.76 tons CaSiO^ and all other treatments in the average of the profile. The high CEC in the soil below 30 cm is probably caused by inherent
properties of the soil, as shown by the X-ray diffraction (Fig.
6 in the Appendix) and also by the movement of basic cations down the profile.
B. Effect of CaSiOj on exchangeable cations in the profile
1) Retention of Potassium
A significant increase in exchangeable K near the surface was obtained as the CaSiO^ rates were increased (Fig. 2). The exchangeable K increased from 91.7 ppm in the control to 276.7
ppm in the plots with 26.88 tons of CaSiOg applied. These
12
4.8 5.2SOIL pH (PASTE)
5.6 6.0 6.4
t/4
Fig. 1. Effect of CaSiOg on Soil pH at Different Soil Depths
Table 1. The effect of CaSiOj on CEC (me/100 g) with depth1
Depth CaSi03 Applied (metric tons/hectare)(cm) 0 6.,72 13.44 26.88 53.76
0-15 48.63 c 50.57 be 53.68 be 55.51 b 63.53 a
15-30 58.29 ab 52.35 b 58.49 ab 56.84 ab 75.94 a
30-46 62.09 a 56.64 a 57.78 a 66.11 a 80.15 a
46-61 64.28 a 74.83 a 60.72 a 65.32 a 71.91 a61-76 76.25 a 87.53 a 68.45 a 68.96 a 86.74 a76-91 84.91 a 73.22 a 77.78 a 89.88 a 86.89' a
Averages of 3 replicates.Averages followed by the same letter are not significantly different from each other at the 51 level.2
0-15
15-30
30-46
46-61
61-76
76-91
EXCHANGEABLE K (ppm)120 180 240 280
T / ■ //
• A
/ /
«-------------------4 0• ............ 6.72©•------------ 13.44e ------------ ----- © 26.88*— --------- 53.76
CaSiO, APPLIED (M.T./ha)
. 2. Effect of CaSiOj on Exchangeable Potassium at Different Soil Depths
increases occurred in the 0-15 cm layer. At the 15-30 an layer, there was a noticeably high retention of K at the higher rates of application (Fig. 2). However, these differences
among all treatments were not found to be statistically
significant. Below 30 cm, the rates of 0 and 6.72 had a considerably higher value for exchangeable K as compared to the rates of 13.44 tons CaSiOj and greater. This indicates that there was less leaching of K with increasing applications of CaSiOy Within each individual treatment, the lower application
rates (0 to 6.72 tons) of CaSiO^, exhibited no significant difference in K content throughout the profile (Table 6 in the Appendix). At application rates higher than 13.44 tons CaSiO^, significant differences in K content appear to occur in layers above and below 30 cm. The leaching of K at the lower rates of
CaSiOj reflects the effect of the significantly lower CEC on the surface layers in these treatments.
/
2) Retention of CalciumThere was a substantial increase of exchangeable Ca with
depth with increasing CaSiO^ rates. The increase at each depth
was significant as far down as the 61-76 cm layer between the
0 and 53.76 tons of CaSiO^ applications (Fig. 3 and Table 8 in the Appendix). The average exchangeable calcium in all depths of the profile show a significant increase from 263 ppm to 2337 ppm between the 0 and 53.76 tons CaSiO^ respectively (Table 14 in the Appendix). On the surface 30 cm the exchangeable Ca increased with increasing rates of CaSiO^ from an average of
16
DEPTH
(cm
)
EXCHANGEABLE Co (ppm X 100)
Fig. 3. Effect of CaSiO^ on Exchangeable Calcium at Different Soil Depths
434 to 4691 ppm with the 0 to 53.76 tons CaSiO^ applied
respectively. On a percent basis, higher percentages of exchangeable Ca in a profile was found at the surface of plots
with higher rates of CaSiO^ applied (Table 9 in the Appendix).
This shows that with the increased rates of CaSiO^, greater
retention of Ca occurs. The increase in exchangeable Ca within a profile resulted from the increased quantity of Ca applied with increasing rates of CaSiO .
Retention of Magnesium
With increasing rates of CaSiO , exchangeable Mg in the surface 15 cm increased significantly from 14.5 ppm to 148.7 ppm with the 0 and 53.76 tons of applied CaSiO , respectively (Fig. 4). This significant difference among rates is visible down to a depth of 61 cm. At the rate of 6.72 tons CaSiO^, a significant increase of Mg occurred with depth but at the rates
of 13.44 tons CaSiO and higher, the results are reversed, that
is, greater amounts of exchangeable Mg was found in the surface 30 cm than at the lower depth. This indicated that at the higher rates of CaSiO^ greater retention of exchangeable Mg occurred at the surface. The low amount of exchangeable Mg at all depths investigated in the control plots may be due to mineral fixation or leaching of Mg beyond the 91 cm depth
(Fig. 4 and Table 10 in the Appendix).
EXCHANGEABLE Mg (ppm)10 25 50 75 100 125 150
Fig. 4. Effect of CaSiOj on Exchangeable Magnesium at Different Soil Depths
C. Water-extractable SiliconWater-extractable silicon increased significantly with increasing
rates of CaSiO^ as far down as the 46 cm depth (Fig. 5 and Table 12 in the Appendix). Beyond this depth, no difference occurred with treatment. This may indicate that significant leaching of Si occurred only to a depth of 46 cm. It also appears that water-extractable Si in the soil constitutes a very small portion of the total silicon applied.
D. Effect of pH of N NH^OAc Extracting Solution on Cation Exchange Capacity and Extractable Cations and SiliconCEC, exchangeable calcium, magnesium and potassium from selected
samples were extracted by two methods: (a) using N NH^OAc adjusted to
pH 7.0 and (b) N NH^OAc adjusted to the pH of the soil. Results obtained
from the test comparing the two methods indicate that there is no significant difference between the two methods in the determination of
calcium, magnesium and potassium (Table 2). However, at rates below26.88 tons/ha of CaSiO , a significant difference between the two methods were observed in CEC. Most of the CEC values determined at the pH of the soil were lower than those determined at pH 7.0. The amount of silicon extracted was significantly higher using N NH^OAc adjusted to
the pH of the soil.
20
DEPT
H (c
m)
H20 EXTRACTABLE Si (ppm)
Fig. 5. Effect of CaSiO^ on Water Extractable Silicon at Different Soil Depths
Table 2. The effect of pH of N NH^OAc on CEC, Extraction of Cations, and Silicon
TreatmentCaSiO,
(M.T./ha) (kg/ha)Depth(cm) pH CEC (me/100 g)
pH-7.0 pH-SoilK (ppm)
pH-7.0 pH-SoilCa (ppm)
pH-7.0 pH-Soil
0 672 0-15 5.01 65.1 ' 48.7 27.0 27.0 23 240 672 15-30 5.21 82.0 53.2 22.2 22.2 18 170 672 30-46 5.56 109.4 91.3 35.4 46.8 18 120 672 . 46-61 5.49 139.9 116.8 42.6 52.2 13 12
6.72 672 0-15 5.35 125.8 49.8 78.0 79.8 416 5286.72 672 15-30 5.44 113.2 51.9 96.0 98.0 432 6006.72 672 30-46 5.56 125.9 55.2 124.0 123.0 416 4726.72 672 61-76 5.78 159.3 108.9 105.0 104.0 384 400
13.44 672 0-15 5.35 76.7 54.6 242.0 250.0 1424 166413.44 672 15-30 5.49 81.7 64.8 253.0 253.0 2016 214413.44 672 30-46 5.10 57.7 67.8 120.0 126.0 1080 132013.44 672 76-91 5.64 58.8 107.8 64.8 69.0 784 832
26.88 672 0-15 5.72 61.4 60.6 316.0 328.0 2960 328026.88 672 15-30 5.85 63.2 64.7 284.0 268.0 3440 340026.88 672 46-61 5.55 76.3 75.2 46.2 51.0 776 87226.88 672 61-76 5.52 72.2 77.2 57.6 70.8 600 648
53.76 672 0-15 6.31 67.7 67.8 166.0 176.0 5280 544053.76 672 15-30 6.00 65.0 69.9 194.0 200.0 4640 472053.76 672 46-61 5.59 60.2 58.3 38.4 47.4 2304 230453.76 672 76-91 6.24 125.7 62.9 26.4 27.6 672 704
r = .320 r = .998** r = .998**
Table 2. (Continued) The effect of pH of N NH^OAc on CEC, Extraction of Cations, and Silicon
CaSiO fke/hal Depth oH Mg (ppm) Si (ppm)(M T /hi) l g J (cm) P pH-7.0 pH-Soil pH-7.0 pH-Soil
0 672 0-15 5.01 5.8 4.8 10.4 43.80 672 15-30 5.21 2.9 3.1 9.0 34.00 672 30-46 5.56 4.4 5.3 4.8 19.10 672 46-61 5.49 4.8 4.6 6.4 27.1
6.72 672 0-15 5.35 12.0 14.0 11.4 27.66.72 672 15-30 5.44 35.0 39.0 8.8 21.26.72 672 30-46 5.56 57.0 56.0 7.4 25.06.72 672 61-76 5.78 54.0 55.0 6.4 23.4
13.44 672 0-15 5.35 62.0 68.0 18.3 33.513.44 672 15-30 5.49 122.5 123.0 13.3 32.913.44 672 30-46 5.10 46.5 . 51.5 9.8 .39.813.44 672 76-91 5.64 64.0 65.0 6.4 18.1
26.88 672 0-15 5.72 102.5 107.5 32.9 43.826.88 672 15-30 5.85 124.0 116.0 41.2 51.026.88 672 30-46 5.55 37.5 38.0 20.2 38.826.88 672 76-91 5.52 31.6 32.0 5.8 24.2
53.76 672 0-15 6.31 155.0 150.0 56.0 55.253.76 672 15-30 6.00 125.0 123.0 48.6 62.753.76 672 46-61 5.59 28.0 25.0 5.8 16.753.76 672 76-91 6.24 21.6 21.0 5.5 15.4
r = .875**
DISCUSSION
The study of the retention of soil exchangeable cations is of great
importance in agriculture, since the mobility of exchangeable bases determines to a great extent the availability of nutrients to plants.
The results presented in the earlier section show the effect of CaSiO^ on soil pH, on CEC and on the retention of basic cations.
Increasing the rates of CaSiOj significantly increased both the soil pH and exchangeable calcium in the profile. The control plots exhibited an increase in soil pH with depth. The acidic condition at the surface may be the result of the hydrolysis of aluminum or the presence
of organic acids. Contrarily, the higher pH at the lower depths may be due to both the inherent properties of the soil or by the movement of
the basic cations down the profile. At the higher rates of CaSiO^
application, 26.88 and 53.76 tons/ha, the pH is higher at the surface than in the subsoil because of the greater retention of the basic exchangeable cations. This increase of pH in the surface soil with increasing rates of CaSiOj is in agreement with works by Bartlett and McIntosh (3) and Mahilum, et al. (25).
Bhumbla and McLean (5) indicated that exchange sites were releasedwhen Al ions were converted to Al(CH)j in limed soils. Mahilum, et al.(25) also found a decrease in exchangeable Al with increasing pH involcanic ash soils. If this is the condition that prevails in this soil,
+2then these exchange sites could be filled with the Ca ions. On the hydrolysis of CaSiO^ the following reaction may occur: CaSiO^ +2H?0 £ Ca(QH)_ + H?SiO,. The concentration of OH ions associated with
the calcium may cause an increase in soil pH. The increase of exchangeable Ca with increasing CaSiO rates correlates with the increasing pH of the corresponding treatment. Organic matter within the
soil behaves as a weak acid with weakly ionized H+ ions (35), which means that the H+ ions can be easily dissociated', replaced with Ca+ ions and
reflect a rise in pH with an increase in CEC.Schofield (35) stated that CEC can be attributed to two types of
charges on clays: (a) permanent charge, in which the magnitude andstrength of charge remains unchanged with pH changes and (b) pH dependent charges, which is weakly acidic in character. In the latter case, with increased pH the H+ ions can be easily dissociated and could possibly
cause the increase in CEC. According to Loganathan (23), soils of the Maile series show a decrease in negative charges with decreasing pH. Accordingly, an increase in negative charges due to the increase in
soil pH, may result in an increase in CEC. The higher CEC values with depth may be caused by the greater surface area at lower depths of the profile where the soil contains amorphous constituents which exhibits irreversible dehydrating material. This is demonstrated by the
increasing soil water content with depth (Table 16 in the Appendix).The surface soil may be lower in CEC owing partly to the susceptibility of being dehydrated into irreversible material, which has a smaller
surface area and charge (21).
The increase of CEC with increasing rates of CaSiO^ in the surface
soil is caused by the increase of pH. This is in agreement with Bhumbla and McLean (5) and de Villiers and Jackson (12) who found increasing CEC
of acid weathered soils or clays with increasing pH. de Villiers and
25
Jackson (12) further explained that the increased CEC with increased pH
resulted from the release of initially blocked isomorphous substitutional
negative charges in clay as a deprotonation of the hydroxy alumina present.
Tamimi, et al. (42) showed that the determination of CEC with N NH^OAc at pH 7.0 did not correlate with the soil pH. However, when determined with N NH^OAc adjusted to the pH of the soil, the results were highly correlated with the soil pH. This shows that the CEC in
this soil is pH dependent. At the rates of 26.88 tons CaSiO^ and higher, the difference in CEC between the two methods become negligible. This
could be caused by the neutralization of negative charges by specifically
adsorbed calcium as described by Syed-Fadzil (41). The extraction of exchangeable Ca, Mg, and K had no significant differences when extracted by the two methods. This indicates that the proper CEC of the soil should be determined at the pH of the soil. By using this method, a
more exact base saturation can be determined. Van Raij and Peech (44) had recently suggested that methods should be modified in determining CEC in some soils as opposed to the use of standard procedures.
High rates of CaSiO^ enhanced the retention of exchangeable K within the surface soil. This is in agreement with results reported by Mahilum, et al. (25). At lower rates of CaSiO^, however, the K content was found to be higher in the subsoil as compared to the higher CaSiO^ treatments. This indicates that greater leaching of exchangeable K
occurred at the lower rates of CaSiO^ which may be due to the lower CEC
at the surface. Tamimi, et al. (42) found that maximum retention of exchangeable K in the surface 15 cm occurred at 53.76 tons CaSiOy The
26
probable explanation for the maximum exchangeable K occurring at the
26.88 tons CaSiO^ in this investigation may be due to experimental error or the limited area of the soil sampled for this investigation.
Exchangeable Ca was found to have substantially increased throughout the profile as the rates of CaSiO^ were increased. This, however, does not necessarily indicate that Ca is readily leached but possibly caused by the large quantity of Ca applied to the plow layer at the high rates of CaSiO * Although leaching took place, a greater percentage of exchangeable Ca was retained in the surface as the rates
of CaSiOj were increased. This retention was possibly the result of increasing CEC with increasing soil pH. Jarusov (20) concluded that the
mobility of exchangeable cations depends on the degree of saturation of the adsorbents with the cation. The increase in pH and CEC with the53.76 tons CaSiO^ treatment can be correlated with the increase in exchangeable Ca down to the 46 cm depth.
All of the plots received a blanket application of 403 kg Mg/ha over the period of the experiment. The application of CaSiO^, which has 0.48% Mg also contributed 4.8 kg Mg/ha which would mean an additional 258 kg
Mg/ha at the 53.76 ton CaSiO^ level. This accounts for the significant/increase of the average exchangeable Mg of the overall profile with increasing rates of CaSiOy However, the data reveal that as the rates of CaSiOy increased, the proportion of the surface retained Mg to the
total amount of applied Mg increases. This indicates that there is
increasing retention of exchangeable Mg in the surface which is again probably caused by the increased CEC with the increasing soil pH.
The increase in water-extractable silicon showed no relation to the increase in pH or CEC when the percent in each layer was taken. The
27
iMW*
28content of silicon seems to be controlled mainly by the amount that is applied.
SUNMARY AND CONCLUSION
The effect of CaSiO^ applied to a Hydric Dystrandept on soil pH, CEC,
exchangeable K, Ca, and Mg, and water-extractable silicon was investigated.
Rates of CaSiO^ applications were 0, 6.72,' 13.44, 26.88, and 53.76 metric
tons/hectare. Soil samples were taken at 15 cm increments to a depth of 91 cm.
With the increasing rates of CaSiO^, there was an increase in soil pH to a depth of 30 cm. The more pronounced increases were at the rates of 26.88 and 53.76 ton/ha of CaSiOy As the soil pH increased, an increase in soil CEC was also observed with increasing rates of CaSiOy
The increase of CEC in the 0-15 cm depth was from 48.63 me/100 g in the control to 63.53 me/100 g in the soil treated with 53.76 ton/ha CaSiOj rates respectively. Increasing the CEC of the soils resulted in a greater retention of K, Ca, and Mg against leaching in the surface
0-30 cm. Six years after the application of CaSiO , silicon had been leached only to a depth of 46 cm.
Twenty samples were used to compare two methods of extraction:(a) N NH^OAc adjusted to the soil pH and (b) N NH^OAc adjusted to pH 7.0.
No significant differences were found between the two methods in the
extraction of K, Ca and Mg. At the lower rates of CaSiO^, CEC determined at pH 7.0 was higher than those determined at the soil pH. However, at
26.88 ton/ha CaSiO^ and higher, differences in CEC between the two methods become negligible. This indicates that CEC determined at pH 7.0 in low pH soils with pH-dependent charges, may be invalid. Since soil CEC increases by increasing the pH of acidic soils, extraction of
exchangeable cations from these soils with NH^OAc at pH 7 would result
in erroneous values for both CEC and percent base saturation.
Results from this study show that liming materials can be used as a
tool in field management for nutrient availability and that the pH of the
extracting solution for CEC and exchangeable cations, presents new
parameters for soil classification. If it is desirable to increase the content of exchangeable K, Ca, Mg or any other cation in the subsoil, low levels of CaSiO^, or any liming material should be used. Also, depending on the buffering capacity of the soil, higher rates of lime could be applied to prevent the leaching of these exchangeable cations.
30
APPENDIX
Table 3. Profile description of the maile silty clay loam (43)32
Horizon: A11(RSL No. 6590)
Description: 0 to 5 cm (0-2 inches), dark reddish brown (5YR 2/2) silt
loam, black (2.5YR 2/1) dry; moderate fine subangular blocky structure;
hard, friable, slightly plastic; many roots; many fine pores; medium acid (pH 6.0): abrupt smooth boundary.
Horizon: A12(RSL No. 6591)Description: 5 to 10 cm (2-4 inches), dark reddish brown (5YR 2/2)
cindery sandy loam, dark brown (10YR 3/3) dry; moderate fine subangular blocky structure; hard, friable; many roots; common fine black cinders and charcoal; medium acid (pH 6.0); abrupt smooth boundary.
Horizon: A13(RSL No. 6592)
Description: 10 to 35 cm (4-14 inches), very dark brown (10YR 2/2)silty clay loam, dark brown (10YR 3/3) dry; strong fine subangular blocky structure; extremely hard, friable, slightly sticky, plastic, smeary; many roots; many fine pores; slightly acid (pH 6.1); clear wavy boundary.
Horizon: B21(RSL No. 6592)Description: 35 to 43 cm (14-17 inches), dark yellowish brown (10YR 3/4)
silty clay loam dark brown (7.5YR 3/3) dry; weak coarse prismatic
structure breaking to moderate fine subangular blocky structure; very hard, friable, slightly sticky, plastic, weakly smeary; many roots; many fine pores; slightly acid (pH 6.2); clear smooth boundary.
Horizon: B22(RSL No. 6594)
Description: 43 to 50 cm (17-20 inches), dark brown (10YR 3/3) silty
clay loam, very dark brown (10YR 2/2) dry; weak coarse prismatic structure breaking to moderate fine subangular blocky structure; very hard, friable, sticky, plastic, weakly smeary; common roots; many fine pores; slightly acid (pH 6.2); clear smooth boundary.
Horizon: B23(RSL No. 6595)
Description: 50 to 60 cm (20-24 inches), dark yellowish brown (10YR 3/4)silty clay loam very dark brown (10YR 2/2) dry; weak coarse prismatic structure breaking to moderate fine subangular blocky structure; very hard, friable, sticky, plastic, weakly smeary; few roots; slightly acid
(pH 6.5); clear smooth boundary.
Horizon: 11C(RSL No. 6596)Description: 60 to 73 cm (24-29 inches), dark brown (10YR 3/3) siltyclay loam, very dark brown (10YR 2/2) dry; structureless, massive; hard, firm, slightly sticky, slightly plastic, weakly smeary; tuff band; few roots; many fine pores; slightly acid (pH 6.5); abrupt smooth boundary.
Horizon: lllB24b(RSL No. 6597)Description: 73 to 90 cm (29-36 inches), dark brown (7.5YR 3/4) silty
clay loam, very dark brown (10YR 2/2) dry; weak medium and fine subangular blocky structure; very hard, friable, sticky, plastic, moderately smeary;
33Table 3. (Continued) Profile description of
the maile silty clay loam (43)
few roots; many fine pores; common patchy glaze; neutral (pH 6.6); abrupt smooth boundary.
Horizon: lllB25b(RSL No. 6598)
Description: 90 to 120 cm (36-48 inches), very dark brown (10YR 2/2)silty clay loam, (10YR 2/2) dry; weak coarse and medium prismatic
structure breaking to moderate medium and fine subangular blocky
structure; very hard, friable, sticky, plastic, moderately smeary; few
roots; many fine pores; common patchy gelatinlike coatings on peds; tuff band about 5 cm (2 inches) thick; neutral (pH 6.6); abrupt smooth boundary.
Horizon: lllB26b(RSL No. 6599)
Description: 120 to 150 cm (48-60 inches), very dark brown (10YR 2/2)
silty clay loam, very dark grayish brown (10YR 3/2) dry; weak medium subangular blocky structure; friable, sticky, plastic, moderately smeary; few roots; many fine pores; neutral (pH 6.6).
Table 3. (Continued) Profile description ofthe maile silty clay loam (43)
Table 4. Chemical analyses of Maile silty clay loam (19)
Depth(in.)
Horizon pH(H20) OrganicCarbon
OrganicMatter
Extrac. Fe %
Extractable Bases (me/100 g) Ca Mg Na K
CEC me/100 g
0-4 Al 4.54 13.97 24.1 14.13 1.83 0.47 ' 0.15 0.18 68.04
4-13 A21 5.00 11.99 20.7 11.67 0.58 0.15 0.15 0.07 72.2513-19 A23 5.41 10.19 17.6 11.75 0.32 0.10 0.11 0.07 66.4119-24 IIB24 5.47 9.39 16.2 10.48 0.14 0.07 0.07 0.05 70.8924-31 IIB25 5.05 7.16 12.3 12.93 0.09 0.07 0.10 0.04 62.3231-42 IIB26 4.95 7.09 12.2 10.33 0.07 0.04 0.08 0.07 68.48
42-51 I IB 27 4.84 6.23 10.7 9.51 0.08 0.04 0.08 0.04 70.2451-59 I IB 28 4.75 6.52 11.2 11.54 0.11 0.08 0.08 0.03 62.22
36
3.33
DEGREE? 2 0
Fig. 6. X-ray diffraction patterns of the Maile silty clay loam profile
Table 5. Hie effect of CaSiO^ on soil pH with depth"*-
CaSiOj Applied (metric tons/hectare)
0 6.72 13.44 26.88 53.76
0-15 4.88 h2 5.12 gh 5.50 efg 5.72 bcdef 6.33 a15-30 5.12 gh 5.35 fg 5.48 efg 5.78 bcde 6.32 a30-46 5.57 cdef 5.53 def 5.48 efg 5.68 bcdef 5.91 bed
46-61 5.57 cdef 5.75 bcde 5.59 bcdef 5.69 bcdef 5.80 bcde61-76 5.48 efg 5.73 bcdef 5.69 bcdef 5.69 bcdef 5.93 be
76-91 5.46 efg 5.81 bcde 5.76 bcde 5.73 bcdef 5.97 ab
^Averages of 3 replicates.2Averages followed by the same letter are not significantly different from each other atthe 5% level.
Table 6. The effect of CaSiO^ on exchangeable K (ppm) with depth-*-
Depth CaSiOj Applied (metric tons/hectare)(cm) 0 6.72 13..44 26.88 53.76
0-15 91.7 efghi2 131.3 cdefghi 258.0 ab 276.7 a 232.7 abc
15-30 149.4 bcdefgh 163.2 abcdefg 215.0 abed 200.0 abede 175.3 abedef
30-46 130.9 cdefghi 132.3 cdefghi 87.3 efghi 68.6 fghi 74.8 fghi
46-61 81.4 fghi 92.9 efghi 57.7 fghi 36.2 hi 57.3 ghi
61-76 97.8 defghi 87.5 efghi 51.5 ghi 40.0 hi 46.2 ghi76-91 79.7 fghi 69.5 fghi 45.3 hi 26.1 i 43.7 hi
^Averages of 3 replicates.2Averages followed by the same letter are not significantly different from each other at the51 level.
*
Table 7. Percent of Total Exchangeable K in each Treatment Profile
Depth(cm)
CaSiOj Applied (metric tons/hectare)0 6.72 13.44 26.88 53.76
0-15 14.5 19.4 36.1 42.7 36.915-30 23.7 24.1 30.1 30.9 27.830-46 20.8 19.6 12.2 10.6 11.946-61 12.9 13.7 8.1 5.6 9.161-76 15.5 12.9 7.2 6.2 7.376-91 12.6 10.3 6.3 4.0 6.9
WVO
Table 8. The effect of CaSiO^ on exchangeable Ca (ppm) with depth^
CaSiO^ Applied (metric tons/hectare)(cm) 0 6.72 13..44 26.88 53.76
0-15 378 ••V!2ljkl 768 ghijk 2016 d 3408 c 5024 a15-30 490 hijkl 1165 efg 1845 d 2915 c 4357 b30-46 259 jkl 931 efghi 869 efghij 1093 efgh 1472 def46-61 187 kl 592 ghijkl 707 ghijkl 856 fghij 1499 de61-76 170 kl 565 ghijkl 641 ghijkl 701 ghijkl 978 efghi76-91 96 1 490 hijkl 510 hijkl 409 ijkl 691 ghijkl
^Averages of 3 replicates.2Averages followed by the same letter are not significantly different from each other at the5% level.
Table 9. Percent of Total Exchangeable Ca in each Treatment Profile
Depth(cm)
CaSi03 Applied (metric tons/hectare)
0 6.72 13.44 26.88 .53.76
0-15 23.9 17.0 30.6 36.3 35.1
15-30 31.0 25.8 28.0 31.1 30.4
30-46 16.4 20.6 13.2 11.7 10.3
46-61 11.8 13.1 10.7 9.1 10.561-76 10.8 12.5 9.7 7.5 6.8
76-91 6.1 10.9 7.7 4.4 4.8
Table 10. The effect of CaSiO^ on exchangeable Mg (ppm) with depth"*"
Depth CaSiOj Applied (metric tons/hectare)(cm) 0 6.72 13.44 26.88 53.76
0-15 14.5 h2 35.7 fgh 90.0 bed 125.2 ab 148.7 a15-30 27.9 . fgh 80.7 cde 100.7 be 120.7 ab 123.0 ab30-46 26.0 fgh 78.8 cde 37.8 fgh 48.3 efgh 41.0 fgh46-61 13.8 h 61.7 def 41.3 fgh 38.0 fgh 31.7 fgh61-76 16.7 gh 51.5 efg 50.7 efgh 27.8 fgh 27.8 fgh76-91 21.5 gh 51.7 efg 41.7 fgh 17.7 gh 20.5 gb
" Averages of 3 replicates.2Averages followed by the same letter are not significantly different from each other at the51 level.
Table 11. Percent of Total Exchangeable Mg in each Treatment Profile
Depth(cm)
CaSiOg Applied (metric tons/hectare)
0 6.72 13.44 26.88 53.71
0-15 12.0 9.9 24.9 33.2 37.9
15-30 23.2 22.4 27.8 32.0 31.3
30-46 21.6 21.9 10.4 12.8 10.4
46-61 11.5 17.1 11.4 10.1 8.1
61-76 13.9 14.3 14.0 7.4 7.1
76-91 17.9 14.4 11.5 4.7 5.2
Table 12. The effect of CaSiO^ on water extractable silicon (ppm) with depth^
Depth(cm)
CaSiOj Applied (metric tons/hectare)0 6.72 13.44 26.88 53.76
0-15 15.8 def2 17.2 de 19.2 cd 26.9 b 34.4 a15-30 13.5 defgh 14.7 defg 1.7.1 de 24.4 be 26.3 b30-46 9.1 fghijk 10.4 efghijk 13.5 defgh 16.8 de 12.6 defghi46-61 6.1 ijk 7.7 hijk 11.6 efghij 9.8 fghijk 8.1 ghijk61-76 5.7 jk 5.6 jk 8.4 ghijk 7.8 hijk 7.6 hijk76-91 5.7 jk 4.7 k 6.9 hijk 6.9 hijk 7.3 hijk
^Averages of 3 replicates.2Averages followed by the same letter are not significantly different from each other at the5% level.
Table 13. Percent of Total Water-Extractable Silicon in each Treatment Profile
Depth(an)
CaSiOg Applied (metric tons/hectare)
0 6.72 13.44 26.88 53.7(
0-15 28.3 28.5 25.0 29.1 35.715-30 24.2 24.4 22.3 26.4 27.3
30-46 16.3 17.3 17.6 18.1 13.146-61 10.9 12.8 15.1 10.6 8.461-76 10.2 9.3 11.0 8.4 7.976-91 10.2 7.8 9.0 7.5 7.6
Table 14.. The effect of CaSiO, on the average pH, CEC, exchangeable Ca and Mg, and water extractable Si of a profile
CaSiO, Rate (M.TT/ha) PH CEC^
(meq/lOOg)Ca(ppm)
Mg(ppm)
Si(ppm)
0 5.35 D2 48.63 C 263 E 20.1 B 9.3 C
6.72 5.55 C 50.57 BC 752 D 60.0 A 10.0 C
13.44 5.58 C 53.68 BC 1098 C 60.4 A 12.8 B
26.88 5.72 B 55.51 B 1564 B 62.9 A 15.4 A
53.76 6.04 A 63.53 A 2337 A 65.5 A 16.0 A
^CEC taken from average of 3 replicates at surface 0-15 cm. All other analyses are averages of 18 observations.Averages followed by the same letter are not significantly different from each other at the 5% level.2
*
Table 15. The effect of CaSiO, on the distribution of exchangeable Ca, Mg, K, and extractable Si in a Profile
IDENTIFICATION MEANS (Average of 15 Observations)No. DEPTH (cm) Ca (ppm) Mg (PPm) K (ppm) Si (ppm) % h 2o
1 0-15 2319 A* 90.6 A 198.1 A 22.7 A 74.98 E2 15-30 2155 A • 82.8 A 180.6 A 19.2 B 136.14 D3 30-46 925 B 46.4 B 98.8 B 12.5 C 195.14 C4 46-61 768 BC 37.3 BC 65.1 BC 8.7 D 209.91 B5 61-76 611 CD 34.8 BC 64.6 BC 7.0 DE 221.76 AB6 76-91 439 D 30.6 C 52.9 C 6.3 E 229.70 A
*P<.05Means followed by the same letter are not significantly different from each other.
" s i
Table 16. Percent Moisture in Soil
Depth(cm)
CaSiO^ Applied (metric tons/hectare)0 6.72 13.44 26.88 53.76
0-15 72.87 77.37 76.49 73.97 74.1815-30 130.45 124.72 120.98 150.68 153.8630-46 207.95 196.40 170.38 211.50 189.4646-61 203.13 200.52 217.29 224.04 204.5761-76 228.47 226.70 217.29 225.00 211.3576-91 248.34 237.13 215.16 224.79 223.08
Table 17. Extractable Soil P by the Modified Truog Method (ppm)
Depth(cm)
CaSiOj Applied (metric tons/hectare)
0 6.72 13.44 26.88 53.76
0-15 24.2 30.2 27.2 24.6 21.5
15-30 13.5 18.2 21.2 11.4 8.1
30-46 3.7 5.2 7.5 4.1 5.2
46-61 4.6 4.3 4.6 3.8 4.0
61-76 4.0 4.3 3.5 3.8 3.5
76-91 3.6 3.9 3.9 2.9 3.2
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«